You must be careful ,becaeuse my micropeltes grow with speed 1cm/week and very fast he became bigger the other fish in my aquarium ,and when he was 25cm long e killed my jardini arowana (aro was 22 cm) ,at 30cm he killed my fosylis catfish (30cm) and after that he killed my antricus ,so ... be careful hehehe
becaeuse my micro had really nasty personality hehehe ...
sometimes it's not giant snakeheads' aggression towards to other fish... because it is such an intense fish it never stop moving and eating it might stress out its tankmates.
since the fish is only 6'' and you got a 180 which is more than enough, i think you'll do fine.
it could work, you will need upgrade cause the snakehead will outgrow a 180 and just remember giant snakeheads are unpredictable and some kill for no apparent reason so you may come home on day with a tank full of dead fish and one snakehead